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Questions on Hawking Radiation

  1. Oct 10, 2003 #1
    I've been reading about Hawking Radiation, and some questions have come up.

    1) What exactly is a virtual particle?
    2) What is negative mass and energy?
  2. jcsd
  3. Oct 10, 2003 #2
    1)I think a virtual particle is one of a pair that pop into and then out of existence like that (*click*,*click*). If they pop up close enough to a black hole, one gets sucked in and the second pop doesn't happen, at which point one floats away. They always occur in opposite pairs ([electron, positron], etc..)
    2)I'm not sure exactly.
    Hope that helps!
  4. Oct 10, 2003 #3
    gee, thanks

    Thank you for the highly detailed explanation.:wink:
  5. Oct 12, 2003 #4

    I don't know what I'm talking about! These are just my vague impressions and memories from some possibly questionable source. Man, if you thought that was detailed you should read the thead I started in the Logic forum (Godel etc.)! You'll notice I quit repling in that one early on, they just kept arguing over almost unrelated semantics! I ended up just thinking what I already thought before I asked. It might have been better placed in one of the physics forums, I couldn't decide.
    EDIT: PS: It just occured to me that you may have been being sarcastic, in which case I feel like the fool I am...
  6. Oct 12, 2003 #5
    just finished feynman's QED.
    1. virtual particles are particles that, as Jonathan said pop in and out of existance without you seing them. let's say you have one photon which is supposed to go from A to B. most of the times, meaning the greatest probability amplitude is that it goes straight from A to B. But that's not all, experiments counting photons going from A to B say. It can also go from A to B but passing through any C point in space, even though C is not on the direct path from A to B. These paths have a smaller probability, but they happen. Also on the road the photon may spontaneously break into an electron and a positron which later recombine to recreate the photon reaching B. It can also break into a moun-antimuon pair or other particle-antiparticle pair. These things can also happen, with an even smaller probability. If the distance from A to B is big it doesn't actually matter that the photon can go in other ways than straight from A to B. Only if you want to get all the decimals right. But if the distance from A to B is quite small, like a few wavelengths it does matter. When stuff becomes "quantum stuff" that's when it starts to matter.
    2. negative mass is the same thing as negative energy, right? and both are something you may end up with by trying to determine the mass of a real particle from its QED behaviour (coupling constant). You usually get infinities. That's why they invented that thing called renormalisation.
  7. Oct 12, 2003 #6


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    a) a virtual particle is the result of taking the uncertainty principle (i.e. ΔEΔt >= h/4π) into account when considering the conservation of mass/energy, this means that pairs of virtual particles may appear and disappear as long as they stay within the uncertainty given by the HUP.

    b) The idea of the black hole swallowing negative mass virtual particles is only one model to describe Hawkings radiation, there's been some disagreement about the ins and outs of this. A real particle cannot have negative mass, so I don't you can say much beyond that it reperesnts a negative flux of energy which results in a loss of mass in a blackhole.
  8. Oct 13, 2003 #7
    "EDIT: PS: It just occured to me that you may have been being sarcastic, in which case I feel like the fool I am..."

    Ya, it was just sarcasm. :wink:

    Thanks for the info guys, that made it all make more sense.
  9. Oct 15, 2003 #8
    Of Virtual Particles and Negative Mass...


    Have u heard of the Uncertainty relation between Energy and Time... It says that the energy transfer and the time taken for the Energy transfer cannot be determined simultaneously. So if the Energy transfer is going to take place really fast then it is not possible to measure this energy. So We can infact break the law of Conservation of energy by actually "creating" a situation where the Energy transferred is so quick that u don't realise that "THE LAW" has been violated. This is the principle of Virtual Particles. These are particles that are generated from nowhere and serve as "messengers of the field". i.e They are assumed to be the source of transfer of energy in a field. The Virtual Partciles are created and are destroyed instantaneously transferring their energy to the nearby space where a new virtual particle evolves and this goes on...
    A Photon is a classical example of a virtual Particle... another example might be the Graviton.....
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